Curl-resistant moistureproof regenerated cellulose film



United States Patent 3,402,063 CURL-RESISTANT MOISTUREPROOF REGENERATED CELLULOSE FILM Joseph C. Mohan, Fredericksburg, Va., assignor to FMC Corporation, Philadelphia, Pa., a corporation of Delaware No Drawing. Filed Oct. 8, 1963, Ser. No. 314,627 7 Claims. (Cl. 117-68) The invention relates to a curl-resistant sheet of hydrophilic, non-fibrous cellulosic material having a resinous moistureproof coating on only one side thereof.

Non-fibrous, hydrophilic cellulosic films such as those prepared from regenerated cellulose which are provided with a moisture proof coating on only one side have a tendency to curl when placed in environments of temperature and relative humidity which are common in commercial packaging operations. It is imperative, in such operations, that the individual sheets and stacks thereof remain perfectly flat for mechanical manipulation.

It is an object of the present invention to provide a composite sheet by hydrophilic, non-fibrous cellulosic base material having a resinous moistureproof coating on only one side thereof which has a greatly reduced curl tendency when placed in commercial packaging environments.

It is another object of this invention to provide a regenerated cellulose film having a resinous, moistureproof coating on only one side thereof which has a greatly reduced curl tendency when placed in commercial packaging environments.

These and other objects are accomplished in accordance with this invention which relates to a composite sheet comprising a base sheet of non-fibrous, hydrophilic cellulosic material, a resinous moistureproof coating on one side of said base sheet, and a layer consisting of a clear, hydrophilic, oleaginous hydrocarbon liquid, uniformly covering the other side of said base sheet in an amount suficient to improve the curl tendency of the sheet.

The base sheet of this invention is any non-fibrous, hydrophilic cellulosic material, for example, regenerated cellulose film and hydroxyethyl cellulose ether film.

The resinous moistureproof coatings for the cellulosic base sheet are well known in the packaging art and include preferably heat-scalable materials, for example, cellulose nitrate containing a moistureproofing wax, monoolefin polymers and copolymers, e.g., polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers; vinyl resins, e.g., vinyl chloride polymers and copolymers, such as vinyl chloride-vinyl acetate interpolymer, vinylidene chloride copolymers; acrylic resins, etc. These coatings are applied, for example, in the form of lacquers or organic solutions, in the form of latexes or aqueous dispersions, by hot melt extrusion onto a moving base sheet, or in any other expeditious manner. Cellulose nitrate compositions and vinylidene chloride copolymers are preferred resinous coatings for this invention.

Clear, hydrophobic oleaginous hydrocarbon liquids of this invention include, for example, natural and synthetic hydrocarbon oils. Natural oils include mineral, animal and vegetable oils. More specifically, natural oils include, for example, refined petroleum oils, castor oil, cottonseed oil, olive oil, peanut oil, corn oil, coconut oil, flax seed oil, palm oil, perilla oil, tallow oil, whale oil, bone oil, and fatty oils derived from natural oils. These oils may be partially hydrogenated to modify their properties, if desired. Synthetic oils include, for example, saturated and unsaturated aliphatic fatty oils containing from 4 to 32 carbon atoms. Mineral oil is a preferred material for this invention.

The hydrophobic hydrocarbon liquid of this invention is applied to the uncoated side of a coated base sheet in the desired amount most advantageously by first mixing the same in an organic solvent or other volatile liquid carrier. The liquid is then applied to the uncoated side of the base sheet and the carrier evaporated. Carriers for the hydrophobic hydrocarbon liquid include toluene, alcohols, ketones, water, etc.

In order to obtain the desired amount of hydrocarbon liquid on the base sheet, a concentration of from about 1 to about 10%, preferably from about 2 to about 6% by weight of the hydrophobic hydrocarbon liquid in the liquid carrier is used. The amount remaining on the base sheet after evaporation of the carrier generally ranges from about 0.1 to about 2.0% based on the weight of the composite film.

The following example is set forth in order to demonstrate the invention.

EXAMPLE A regenerated cellulose film having a thickness of about 1 mil coated on one side thereof with a moistureproof cellulose nitrate coating composition having a thickness of about 0.25 mil, was treated by applying a liquid film of a mineral oil at a concentration of 4% in toluene, to the uncoated surface thereof. The toluene was evaporated, leaving a film of the mineral oil in an amount of about 0.75% based on the weight of the composite film. The resulting film was cut to form 15 inch by 15 inch sheets and stacked in a SOD-sheet pack. At 21% and 31% relative humidity the stacked sheets showed only a slight trace of curl while untreated film in similar stacks showed a bad tendency to curl.

Various changes and modifications may be made practicing the invention without departing from the spirit and scope thereof and, therefore, the invention is not to be limited except as defined in the appended claims.

I claim: v

1. A composite sheet comprising a base sheet of a non-fibrous, hydrophilic cellulosic material, a resinous moistureproof coating on only one side of said base sheet, and a layer consisting of a hydrophobic, oleaginous hydrocarbon liquid uniformly covering the other side of said base sheet in an amount sufficient to inhibit the curl tendency characteristics of the sheet.

2. A composite sheet comprising a base sheet of a nonfibrous regenerated cellulose, a resinous moisture proof coating on only one side of said base sheet, and a layer consisting of a clear liquid selected from the group consisting of mineral oil, vegetable oil, and animal oil uniformly covering the other side thereof in an amount sufficient to inhibit the curl tendency of said base sheet.

3. A composite sheet comprising a base sheet of nonfibrous regenerated cellulose, a resinous, heat-scalable, moistureproof coating on only one side of said base sheet, and a layer consisting of mineral oil in an amount ranging from about 0.1 to 2.0% based on the weight of the composite sheet uniformly covering the other side of said base sheet.

4. The composite sheet of claim 3 wherein the moistureproof coating is a cellulose nitrate composition.

5. The composite sheet of claim 3 wherein the moistureproof coating is a vinylidene chloride copolymer.

6. The composite sheet of claim 3 wherein the moistureproof coating is polyethylene.

polymer.

References Cited UNITED STATES PATENTS Wilson 117-68 Kallock 117-145 X Silsby 117--145 X Learn 117145 X 11/ 1957 Nadeau 117'68 X 9/1962 McKillip et a1 117-68 X 12/1965 Rosser 11768 X l/1927 Poorman 11736.3 3/1937 Cohoe 11736.3

FOREIGN PATENTS 2/1958 Great Britain.

MURRAY KATZ, Primary Examiner. 

1. A COMPOSITE SHEET COMPRISING A BASE SHEET OF A NON-FIBROUS, HYDROPHILIC CELLULOSIC MATERIAL, A RESINOUS MOISTUREPROOF COATING ON ONLY ONE SIDE OF SAID BASE SHEET, AND A LAYER CONSISTING OF A HYDROPHOBIC, OLEAGINOUS HYDROCARBON LIDQUID UNIFORMLY COVERING THE OTHER SIDE OF SAID BASE SHEET IN AN AMOUNT SUFFICIENT TO INHIBIT THE CURL TENDENCY CHARACTERISTICS OF THE SHEET. 